The minerals sector has been under increased pressure in recent times to minimize water consumption. Many mining operations are located in remote, dry areas, where water is scarce. Accordingly, water conservation can be critical to ensure the viable operation of a mine and typically entails use of groundwater and/or recycled water in process operations. Other mines may be located near the coast where seawater may be used as the process water. As a consequence, process waters will usually inherently contain dissolved salts, which can vary from mine to mine and even over the course of a single mine operation. In some locations, the process waters can be highly saline, such as in excess of 100 g/L.
Process waters having high or variable salinity can be problematical in downstream operations, particularly during the extraction of target metals by solvent extraction or ion exchange. This can be due to lack of selectivity for the target metals over chloride ions and other dissolved impurities (such as ferric ions). Without wishing to be limited by theory, it may be that the metal chloride complexes are more problematic to separate effectively, compared to their sulphate counterparts. In the case of solvent extraction, chloride and other impurities may load into the organic phase together with the target metal, either as an elemental ion or as chloride complexes, requiring their subsequent removal. In extreme cases the chloride and other impurities can preclude or retard the uranium loading. Moreover if the salinity of the pregnant leach solution varies over the course of a leaching operation, the details of the extraction process may need to also vary in response.
There is accordingly a need for a process for recovering uranium from chloride containing process waters which overcomes, or at least alleviates, one or more disadvantages of the prior art. There is also a need for an effective process for recovering uranium from chloride containing process waters which also contain high iron and sulphate levels.
There is further a need for such a process which can be easily modified/adapted to accommodate variations in the chemistry of process waters either between plants or within a particular plant over time. An example is where the salinity of the process waters within a plant increases over the course of an operation due to process stream/water recycling, increasing salinity of the groundwater or the inclusion of an alternative more saline source of water such as sea or bore water.
The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the process as disclosed herein.